Butterflies adapted to Climate Change?

Our species of butterfly and moth, collectively known as Lepidoptera, are perfectly adapted to survive in our UK climate but many species are only able to make use of certain parts of the country due to temperature and/or habitat.

Butterflies, and moths to some degree, are often used as indicators of climate change as they are very sensitive to climate variables. Temperature strongly effects butterflies so it makes sense that you can see climate change effects through changes in the butterfly populations in an area.

Species at the northern limit of their ranges for instance have been able to expand their ranges, moving northwards throughout the UK. Orange-tip and Peacock have become common in Scotland as the climate has become more suitable with this being linked to climate change.

Peacock butterfly moving North

The Cinnabar Moth, a day flying moth, was at its furthest range at St Cyrus for some time but was recorded at Forvie NNR in 2009 and is now regularly recorded on the Reserve clifftops.

Cinnabar Moth on Forvie NNR clifftops

Migratory species of butterfly like the Red Admiral have adapted to the climate with wintering populations now found in the UK.

Speckled Wood – another species moving further North

Another adaptation being employed to deal with the changes in climate is to start emerging earlier in the year in line with the climate. The beginning of the year in 2019 was much warmer than the same time period in 2018. This brought with it earlier species records of butterfly. In this way, many species of butterfly or some moths can almost look like they are extremely well equipt to deal with climate change. Move North and/or start your life cycle earlier to match the climate.

On the flip side of this there are some species that cannot adapted at this pace like the High Brown Fritillary and Silver-Studded Blue. Not species you see at Forvie mind you but they are specialised species. They have more particular habitat requirements and can be isolated on fragments of suitable habitats. These habitats are like small islands in a sea of agriculture and urban development. Due to their specialism, they cannot adapt quickly enough to keep up with the climate. In response to this though are some amazing projects though focused on wildlife corridors, connecting bits of isolated habitat to help stabilise and spread populations, particularly for habitat specialist that are more prone to population fragmentation.

All in all there will be some positive and some negative impacts with climate change, each having a separate influence dependant on the species and habitats. The story of the Peacock spreading is similar to that of the Robins and the Blackbirds of the bird world. The Generalists survive. The Peacock butterfly fairs best in the face of habitat loss and climate change as it can survive on more varied habitats. In this case, the Peacock butterfly establishing further north did so in part by making use of our gardens, the “small islands” we’ve provided in the sea of urban development. So never forget the importance of your garden in the bigger picture of wildlife biodiversity, every little green space is important.

A history in the land – Forvie’s Geology

Author Richard Woods – Forvie Volunteer

The diversity of wildlife and habitats at Forvie is due to several factors, including the climate and the shape of the landscape. The geomorphology is a result of the geological processes which have been acting for hundreds of millions of years. The sea and weather continue to change the coastline relentlessly. Three of the most obvious features of this landscape are the estuary of the river Ythan, the southern sand dunes, and the rocky coast in the northern half of the nature reserve.

The Ythan Estuary
The river Ythan flows for about 60 km (37 miles) through Aberdeenshire, reaching the sea on the southern edge of the nature reserve where it forms a small, shallow estuary. Here, the riverbed is a mixture of gravel, sand and mud which provides an ideal habitat for thousands of wading birds.

Ythan Estuary at low tide looking South (downstream)

During the last ice age, 27000 to 12000 years ago, the sea level was about 120 metres lower than it is today. As the climate warmed, the present-day estuary would have been a deep valley filled with glacial meltwater. The sea level rose, but so too did the land (though much more slowly) as the weight of the overlying ice was removed. The sea invaded the valley which gradually silted up, forming a shallow estuary. The changes in sea level also created a series of raised beaches which can still be seen on the reserve.

Up to eight raised beaches have been identified at Forvie, the most obvious being about two, five and ten metres above the present sea level. The path along the estuary from the Waterside car park roughly follows the 2-metre beach, and the 10-metre beach is now a sheep field above the path.

The 5-metre raised beach is best seen on the path between the estuary and the sea, among the dunes at the southern end of the reserve. It is also exposed near the mouth of the river Ythan where it forms an ideal nesting ground for the tern colony. The pebbles on this beach show a variety of textures and colours, most appear completely different from the local bedrock. These came from rocks which are found many miles inland and would have been transported here by glacial meltwater. Important to note that this section of the reserve is closed to the public during the breeding season for the terns with the Southern tip of the reserve protected all year for the designated Seal haul-out. Please follow all signage and barriers on the reserve when present.

Raised beach, partially covered by sand dunes
Pebbles on the raised beach; most are different from the local bedrock.

The Sand Dunes

The large sand dune between the estuary and the sea dominates the south of the reserve and is part of one of the largest dynamic dune systems in the United Kingdom.

Sand from a vast glacial deposit on the seabed is brought ashore by marine currents and waves at the southern end of the reserve, near the mouth of the river Ythan. The prevailing onshore south-easterly wind then blows the sand up the beach to form a dune up to 30 metres high, which moves steadily northwards. Few plants can grow in such an unstable environment, so the sand is free to move. Much of the sand from this ‘big dune’ ends up in the river Ythan and is washed back out to sea, forming a continuous cycle. The dune changes visibly in height and shape from one year to the next; winter storms expose the shingle of the raised beach at the base of the dune, sometimes revealing old vehicle tracks and vintage beach litter deposited several decades ago, before the dune engulfed them.  

Over the last four thousand years, a succession of dunes has advanced northwards, driven by the onshore wind. Their progress has been deduced from archaeology and historical records: two thousand years ago, Iron Age fields in what is now the south of the reserve were covered by several feet of wind-blown sand; in 1413 Forvie Kirk and village (in the middle of the reserve) were overwhelmed; in 1680 wind-blown sand covered the whole parish, the dune front reaching the northern lochs (near the reserve’s visitor centre); and in 1759 farms at Cotehill and Collieston applied for tax relief to compensate for the effects of the sand which covered their fields.

Eventually the movement of the northern dunes stalled as they moved too far from their supply of sand. Today, the dune system forms a series of seven ‘waves’, with lower-lying ‘dune slacks’ between them. The ‘big dune’ at the southern tip of the reserve is the youngest and most active.

The ‘Big Dune’ encroaching on older, grass-covered dunes

To the north, the dunes become progressively older and more stable. Pioneer plants such as Marram grass bind the sand, allowing other species to gain a foothold and soil to form.  The northern end of the reserve is covered by heather and scrub which gives little indication of the sand lying beneath.

Older dunes with more mature vegetation established in the low-lying ‘dune slack’

The Rocky Coast

The sandy beach, which stretches 20 km (12 miles) from Aberdeen to Forvie, ends abruptly at Rockend about half-way along the reserve’s coast. A dipping layer of grey rock emerges from the sand, initially forming low cliffs which become progressively higher, reaching a height of about 40 metres at Collieston, at the northern edge of the reserve.

View northwards along beach with the cliffs at Rockend in the distance

The waves and weather exploit any weakness, and at Rockend the rocks tend to break into parallel-sided blocks. Some, larger than a refrigerator, indicate the power of the winter storms.

Rock outcrop showing parallel fractures
Rock outcrop at Rockend

At first sight these rocks might appear unremarkable, but they have an interesting story to tell. They belong to a geological group called the Dalradian and were once ocean sediments which were deposited about 550 million years ago. These were later compressed, baked, and folded by immense forces to form ‘metamorphic’ rocks as ancient continents collided, the ocean was destroyed, and a mountain range was formed and eroded.

Traces of this violent past, such as folds and faults in the cliffs, are visible today. Minerals and structures within the rocks indicate the extreme temperatures and pressures which they have endured.

Pressure and heat fold the rock. A small ‘S-shaped’ fold in the cliff face.

To the north of Rockend the cliffs are home to seabirds, ravens, and peregrines. Waves and weather have formed natural arches and stacks with evocative names such as the Needle Eye, Corbie (‘crow’) Holes and The Poor Man. The shaping of the coastline never ceases.

This short tour of the coastal geomorphology of the reserve has shown some of the major features to be found within a small area. The estuary, dunes and rocky cliffs, and the processes which formed them are of scientific interest in themselves; the habitats they provide support the diversity of plants, birds and other wildlife which live here.

Hardy coastal plants

One of the features that makes Forvie special, like much of the North East coast, is the coastal morphology. The cliffs of Forvie are a protected feature of the site and it’s an important habitat on its own right. The environment is harsh, bearing the brunt of strong winds, breaking waves and salt spray. Yet they are home to plenty of wildlife, our coastal specialists!

Forvie’s coastal morphology

Some of the species that might instantly jump to mind are our seabirds like thyis Kittiwake below pictures last year. Many species will nest on the cliffs to stay away from predators like foxes but herin lies the trade off. There is a reason they are safer from certain predators on the cliffs, the danger and harshness of the environment. These birds are specially adapted to live in these environments, filling a different niche than species we might see inland.

Wildlife on the cliffs – Kittiwake with chick

But birds are not the only groups that have adapted to these niche environment. These are also harsh conditions for plants, on the cliff and clifftops. The physical elements are challenging. Strong winds prune plants of leaves and dry them out. Rocky and sandy soil limit water retention. Waves crashing over the cliffs spray salt in the air that absorbs into the plants – all things that would kill many plants.

Waves breaking over the cliffs spraying salt water

Yet as the title suggests, our coastal specialist are hardy plants! A familiar sight for many on the cliffs will be Sea Thrift. You will often see bees fliting from flower to flower on the Forvie cliffs picking up nectar and pollen along the way. One of the features that allows it to grow on the clifftops is that it’s a halophyte, meaning it is adapted to varying saline conditions. Salt taken up into the plant is compartmentalised and sent into older leaves of the plant which will be shed from the plant. It is also drought tolerant, meaning it will grow well on coastal habitats but in poorly drained soil that holds a lot of water, Sea Thrift would likely be out-competed by other plants.

Sea Thift in full bloom
Sea Thirft flowering head

Another coastal specialist we have on the Forvie coast is this beautiful flowering Sea Campion. As the name suggests, just like Sea Thrift, it occurs mostly by the sea and grows on the clifftops on the reserve. Sea Campion’s grey-green leaves are slightly fleshy which helps it to retain moisture in the face of sea winds. The leaves are also waxy to feel, this is often a feature of plants to help retain moisture in the leaf.

Sea Campion

One of the rare and protected plants at Forvie which is a true coastal specialist is the Oysterplant pictured below. It blooms beautiful blue flowers, pink when in bud. It forms mats on the shingle and even from the picture you can tell the leaves are quite fleshy to help store water! It got its common name as its leaves are said to taste of oysters. As it’s a protected plant we can’t of course test that so we might have to trust the internet on that one. They are also called Sea Bluebells as the flowers do share a resemblance! On the reserve these plants can grow on the high tide line, washed over with sea water and wave action. The lack of other plants nearby shows just how specialised and tough plants like this can be but they do suffer. Its rarity these days stems from habitat destruction and climate change.

Oysterplant – a protected species on the reserve.

This last plant grows in coastal areas like clifftops and salt-marshes but can occur other places as well. Common Scurvy-grass. To avoid confusion, it didn’t get its common name because it leaves you anaemic with severe tooth issues but quite the opposite. It is rich in vitamin C and was brought on ships in dried bundles or as extracts to stave off scurvy. The sharp taste of the leaves were made into a popular Scurvy-grass ale in the UK as a tonic. That might just be another flavour that I’ll leave to my imagination. Like the other plants here, it has a high tolerance to salt levels which allows it to grow better in unforgiving coastal conditions.

Common Scurvy-grass

All in all the species found on the coast are often specially adapted to this environment, hence why they thrive as opposed to other species. These species are just some of the plants that brave the elements to adapt to their local environments.

Nesting habits

It’s that time of the year again, your garden birds are getting busy and collecting nest material for the season ahead. The dawn chorus a beautiful sound scape in the early hours, if you’re the type to be up that early!

Over the last while I’ve watched some of my garden birds gather nest materials, eagerly hopping around on the ground collecting foliage, small twigs, feathers… the whole shabang really.

Starling gathering materials for a nest

I’ve been lucky enough to get a Willow Warbler singing in my garden everyday too! Unfortunately this good luck has been balanced out by a nesting pair of Starling in the gutter above my bedroom window….. the scratching and calling a 5am has been a very consistent alarm clock recently.

Willow Warbler proudly singing away in the tree tops

Although a lot of birds nest in trees as you would expect many also nest in bushes and hedgerows.

flimsy wood pigeon nest build from twigs

With this in mind and with many of us out gardening in the current crisis its important to not forget that any tree or hedge work should be avoided at this time of the year! All nesting birds are protected in the UK so there is a risk of disturbing or destroying nests with tree or hedge work during the breeding season.

The beginnings of a blue tit nest in a nest box

My garden birds prepping for the season got me thinking about other species that I am missing at home, the diversity in how birds nest can be quite interesting! Our reserve resident terns and Black-Headed Gulls for instance opt to nest on the ground in large colonies. Although non breeding on reserve, waders like Lapwing nest in a similar fashion in some regards, relying on safety in numbers. They in particular look to nest in very short cropped vegetation in wide open areas like fields to limit any hiding spaces or perches for predators. Trees that might be too near could rule out a nesting location for Lapwing, a potential perch for a buzzard to prey on the colony.

Eider take another approach, relying on camouflage and nesting in the vegetation. They stay perfectly still if they think you haven’t noticed them to protect their eggs.

Female Eider incubating eggs

One of the first birds that shocked me was they Grey Heron, turns out they nest in trees! Being a waterbird I never really associated them with trees but they do nest high up in the canopy. Heronries can be found in reedbeds too which I suppose is what I had assumed initially, at least I wasn’t totally incorrect.

Grey Herons nest up trees

Two other surprising species are Puffins and Shelduck. Both birds can actually re-purpose old rabbit burrows to nest underground! Surprising enough as I found this, the biggest surprise came last year seeing a single Jackdaw flying in and out of the ternary, entering with a full crop and leaving with an empty crop. After investigating the site to ensure there wasn’t any predation issues the only thing we found was a number of old rabbit holes…. we came to the conclusion that like a Puffin or Shelduck, the Jackdaw was probably making the most of the available space underground to make its nest.

Osprey being chased off by shelducks

Seabird Season 2019

Another update about the breeding season from some of our key species! This one focusing on our cliff nesting seabirds in 2019. For those of you who might be less familiar with the reserve we have a small number of seabirds on the cliffs from Collieston all the way down to Rockend where the cliffs give way to beach.

The number of Kittiwakes nesting at Forvie has varied considerably over the years, with a steady decline in the late 1990s/early 2000s being followed by a partial recovery, since then numbers have fluctuated from year to year. This year we identified 387 nests which is a drop from last year but overall a fairly average total for this site in relation to the previous few years!

Fulmar numbers have also fluctuated widely at Forvie from one season to the next, with a breeding population of between 180 and 360 pairs in most years. The long-term trend has been for a slow decline since the late 1990s. This years census found only 56 fulmar sites the lowest total since recording began on site in 1986. The previous lowest total has been very recently in 2016 with 73 nest sites. There were higher numbers than previous years of fulmars loafing around on this cliffs not on nests so perhaps there was a chance for some late breeding attempts here to boost these numbers.

Both Guillemots and Razorbills breed at Forvie in small and relatively recently-established colonies. Both species increased steadily in numbers from the late 1990s up to 2012, and have fluctuated slightly from year to year since. 2019 seen an increase in both species over the previous year with 148 razorbills and 59 guillemots!

The Cormorant colony was first recorded at Forvie on this monitoring programme in 2002, with numbers increasing to a peak of 93 nests in 2006. Since then the population has become very variable between seasons, and the colony was abandoned altogether in 2017. 2018 seen the return of 2 nests but this season recorded no Cormorant nests in 2019. It would appear that there is an exchange of birds between local colonies each year, including one just to the north of Collieston village (personal observations of Daryl Short) so no nests this year does not mean that cormorants are not having a good year overall.

Two pairs of Shags nested at Forvie in 2019, both at the traditional nesting site on the stack at the Corbie Holes (unfortunately we don’t have any pictures of shags). This particular site has been occupied by a single pair most years since at least 2000! A second pair has been present in recent years since 2014.

Herring gulls on site have undergone an alarming decline between 2010 and 2011 (315 to 144 nests). Although the herring gull population somewhat recovered in the subsequent seasons the decline continued reaching the only 37 nests in 2019, and sharp decline from the 63 nests in 2018. Similar to Fulmars, this is the lowest breeding population recorded since surveying began in 1986, exceeding the previous low in 2016 of 45 nests. Since surveying began at Forvie in 1986, the breeding population of Herring Gulls has declined by some 95%.

For the ninth consecutive year, no Lesser Black-backed Gull nests were recorded, and no adults or immature birds were noted on the day of the survey. Although loafing birds can still occasionally be seen at Hackley Bay this species has become locally scarce in recent seasons.

One Great Black-backed Gull nest was located pictured above! We were lucky enough to see the little chicks around their nest area on top of a sea-stack, taking its place at the top, definitely an apex predator in the colony of seabirds. The numbers of GBBGs have been low at Forvie for some time, back in 2007 there were 7 nesting pairs but this year and in 2017 seen only one nest. Like with the other species the reason for the species relative scarcity in recent seasons is unclear, but there has been a distinct decline since seven nests were recorded in 2007.

All in all, the census for the seabird season provided some positive news but mostly a continuing trend of worrying news. Some of the species are holding their own, but species like fulmar and herring gull suffering further declines, peaking with their lowest nesting season yet. With the proximity of the tern colony on the south end of the reserve which overall is doing extremely well, food supply for the cliff nesting seabirds was likely not a problem as it seems to pose no issue for the terns which share much of the same food supply. When looking at these population trends like our loss of cormorants on site for example its important to take in the bigger picture. While it is a decline for cormorants at Forvie, further north along the coast might see an increase, so that bigger picture needs to be taken into account. We send all our data into JNCC as do other sites so that a full image of how the seabirds are doing can be assessed! This will help us understand how our seabirds are really doing looking into next season.

Forvie eiders season

Eiders and the Ythan estuary have a steep history. As many of the locals know, there was a time that Forvie hosted the largest population of breeding eiders in the UK! Back in 1991 the spring peak population of eiders on the Ythan reached over 5000 birds.

Dating even further back the spring population of eiders grew from 3500 in 1961 to a maximum of 6700 in 1984. Since then the population fluctuated, sometimes substantially, but the dramatic decline of our sea duck began in 2005.

The eiders synonymous with Forvie

In 2005 there were over 5000 birds which by 2008 had dropped to just 2130 eiders. Since then there has been an overall steady decline. But where are we now? Having just prepared the 2019 eider report, we have had the chance to summarise the data gathered during surveys.

The 2019 breeding season has seen the lowest spring population of eiders in at least the last 58 years (could not find any older reports!) with only 1323 eiders. The last 6 or 7 years has seen on average a 5% decline year on year and this year and on the face of it this year has continued on this trend. The eiders of Forvie are still struggling to stabilize at a sustainable population. They are an iconic species on the reserve and it is sad to think the cooing along the estuary will continue getting quieter and quieter.

But is it all doom and gloom?

Part of the monitoring for eiders on reserve includes not only counting the peak population on the estuary and along the coast from Collieston to Newburgh but also nest searches and duckling/fledgling counts.

A nesting female counted as part of the annual census

We found a total of 97 nests and later in the season 86 eider ducklings reached the fledgling stage. From here they will have a high survival rate, capable of flight to protect themselves. While Forvie had the lowest spring peak population, the breeding output and the number of fledged eiders in 2019 is marginally better than the previous three years. 86 fledged birds from 97 nests is actually quite a positive result! Particularly for long lived birds like eiders.

Some of the ducklings from this year

On top of this, although the spring peak population in total was at its lowest, the number of potential breeding females was higher than the previous three years! Normally the males outnumber the females quite heavily but this ratio can fluctuate quite a lot between years and this year seen then low end of that ratio. Likely a large portion of the missing males have been further north or south around other colonies.

So all in all, the eiders at Forvie had a promising year compared with the past few seasons. Coming into next year, hopefully we will see the return of many of the same eiders, the colony bolstered with the 86 ducklings fledged in 2019.

On a final note, food for thought on the eiders at Forvie. 86 fledged birds from 97 nests is an excellent result but why are there so few nests? This year seen almost 400 adult females on the Ythan at its peak. Skipping a breeding year for an eider is not uncommon to improve its own survival but only 1 in 4 decided to nest. This has been happening for a number of years consecutively. Considerable research has gone into the eiders at Forvie studying body condition of individuals, ringing projects, studying food supply etc. but unfortunately there hasn’t been a conclusive problem identified. This is undoubtedly a complex problem, and the the underlying stress around the future of the eider colony.

Forvie’s dynamic dunes

Forvie NNR host the tail end of one of the largest Sand Dune systems in the UK. The Dune system begins from near Aberdeen city up along the coast past Balmedie, Forvern Burn and half way through the Forvie NNR reserve before giving way to coastal cliff.

The Big Dune at Forvie NNR – a free moving dune slowly shifting North

As hard as it is to imagine, these “shifting dunes” true to their name are mobile. The dunes move with the prevailing wind, sand added and recycled from far off the coast driven by the tide.

Since starting my position at Forvie I’ve been fascinated with the dunes. The southern end of the reserve is dominated by a large expanse of sand slacks and sand dunes, partially visible in the photo above. A bleak, lifeless environment on the surface but one of stark beauty which bursts to life with the arrival of the terns and gulls for breeding.

Over the last few months here I’ve met a number of wonderful folk that have previously worked here, my predecessors on the reserve. Each of them would mention after after many years of not seeing the dunes they can’t believe how the landscape has changed. I’ve had a glimpse of this recently through an old photo of the seal haul-out that was shared. At the time we did not know how old this photo was but we took another snap from roughly the same location to compare the changes.

Old photo (Lorne Gill) – Ythan mouth from Newburgh beach
Current photo (Sep 2019)

The pill box has gone from being almost completely buried to being totally exposed – that’s a shift of at least 2-3 meters of sand deep being moved. Enough sand has been shifted to expose rock on the seal haul out where non was visible before.

Looking further into the background there is now an imposing ridge of sand with a drop onto the beach. All in all, who know how many thousands of tonnes of sand shifted changing the landscape. In the end the old photo was only taken in the summer of 2016 so this change occurred only over the last 3 years!

Even in my 5 months here, it sometimes seems to change overnight. I notice small changes over time but occasionally I find myself seeing new paths through the dunes wondering if that was there as I walked through yesterday, climbing a dune thinking this seems more steep – or was it my imagination? The dunes a labyrinth of sand, a puzzle being reworked by the wind.

These photos sparked a new appreciation for the dunes in me and their importance. Why is this dynamic nature needed on the coastline? Outside of the unique habitat that dunes create for flora and fauna, they act as a barrier against the seas. They are a natural defense against rising sea levels and given the current climate emergency they are becoming only more important on our coast, protecting inland areas from the seas and storms. Dunes are not our only natural defense on the coast. Cliffs protect inland areas from storm waves and wetlands reduce flood risks. In the end, I am all the more thankful for the dunes and our natural world here at Forvie.

Forvie NNR sand dunes – our natural defense ©Lorne Gill/SNH